1. Field of the Invention
The field of art to which the claimed invention pertains is the catalytic cracking of hydrocarbons. More specifically, the claimed invention relates to an FCC catalyst composition containing acid treated kaolin or metakaolin clay.
2. Description of the Prior Art
Several proposals for the treatment of kaolin clay with a mineral acid have been put forward by the prior art.
In the prior art several thermal and chemical treatments are described for kaolin clay to be added to catalyst compositions to obtain improved catalyst characteristics. It is known from prior art that clay, due to its reasonable price and availability, constitute a particularly suitable FCC component.
The dealuminization of kaolin to produce a suitable porous substance for adding to catalyst compositions was the subject of GB 2,118,063, in which Was described the preparation of a binder obtained by treating metakaolin with hydrochloric or nitric acid or aluminum chloride, with such an acid reacting with up to 25 mole % of the structural alumina in the metakaolin.
GB 2,120,571 also describes the acid leaching of kaolin to be added to catalytic cracking compositions. The metakaolin is leached with hydrochloric acid and then spray dried; it may subsequently be ion exchanged. However, acid leaching with hydrochloric or nitric acid only leads to a reduction of the alumina content of the product and does not provide for the precipitation of certain aluminum salts which might contribute catalytic activity.
EP 0 240 136 discloses kaolin washed with a mineral acid which is physically mixed as separate particles with an FCC catalyst to function as a nitrogen scavenger. No catalytic activity is attributable to the acid treated kaolin. U.S. Pat. No. 3,406,124 relates to the preparation of a composite catalyst comprising crystalline aluminosilicate, in which preparative process an alumina containing clay is leached and subsequently precipitated in situ by neutralization. Such a preparation renders the clay useful as a binder in catalytic compositions.
It should be noted that from U.S. Pat. No. 3,437,441 an acid treatment of kaolin with sulphuric, phosphoric or acetic acid is known. However, this reference provides no hint to using this kaolin in an FCC catalyst composition.
The present invention is based on the discovery that when the kaolin or metakaolin clay is acid treated with particular mineral acids in a novel manner, the FCC catalyst which contains the acid treated clay will exhibit superior performance.